How do I register C&C Tiberium Twlight on a used serial no on crashed hard drive

My previous PC hard drive crash and this had on it registered version of Command and Conquer Tiberian Twilight - so after creating a new EA account and signing on when I use existing serial number it states it is already in use. Well yes I know that but as the old hard drive unusable and therefore cannot unregister how do I resolve this?